1. Field of Invention
The present invention relates to a method for manufacturing a semiconductor device. More particularly, the present invention relates to a method for manufacturing a dynamic random access memory having deep trench capacitors.
2. Description of Related Art
Dynamic random access memory (DRAM) is a semiconductor memory. It consists of transistors and capacitors wherein capacitors are used to store charges and one of the capacitors usually used for DRAM is called a trench capacitor.
The so-called trench capacitor is a type of capacitor arranged in the substrate. In the process of manufacturing trench capacitors, a substrate is dry trenched by plasma first to form trenches in the substrate, and then the capacitors are arranged in the trenches. In order to increase the capacity of trench capacitors, the trenches in the substrate are usually deep. These are called deep trench capacitors. However, in the process of manufacturing deep trench capacitors, sometimes defects are found in the deep trench structures. This causes the deep trench capacitor to lose the function of storing charges which will affect the quality of the semiconductor devices.
For the forgoing reasons, it is an important issue to eliminate defect sources in the process of manufacturing trench capacitors to reduce defects and to improve the quality of products.